add partial render method

This enables the user to render partial templates to embed them into
other templates and the like.

lib/zero/renderer.rb

@@ -71,19 +71,26 @@ module Zero
     # @return [String] the result of rendering
     def render(template, types, context)
       unless templates.exist_for_types?(layout, types)
-        return load_template(template, types).render(context) 
+        return render_partial(template, types, context)
       end
       load_layout_template(types).render(context) do
-        load_template(template, types).render(context)
+        render_partial(template, types, context)
       end
     end
 
+    # render a template without layout
+    #
+    # This can be used to render a template without using a layout.
+    # @param template [String] the template to render
+    # @param types [Array<String>] a list of types requested to render
+    # @param context [Object] any object to use for rendering
+    # @return [String] the result of rendering
+    def render_partial(template, types, context)
+      templates.get(template, types).render(context)
+    end
+
     private
 
-    def load_template(template, types)
-      templates.get(template, types)
-    end
-
     def load_layout_template(types)
       templates.get(layout, types)
     end

spec/fixtures/templates/layout.html.erb

@@ -0,0 +1,3 @@
+layoutfile
+
+<%= yield %>

spec/unit/zero/renderer/render_partial_spec.rb

@@ -0,0 +1,53 @@
+require 'spec_helper'
+
+describe Zero::Renderer, '#render' do
+  subject { described_class.new(template_path, type_map) }
+  let(:template_path) { 'spec/fixtures/templates/' }
+  let(:type_map) {{
+    'html' => ['text/html', 'text/xml', '*/*'],
+    'json' => ['application/json', 'plain/text']
+  }}
+  let(:html_types) { ['text/html'] }
+  let(:json_types) { ['application/json'] }
+  let(:foo_types)  { ['foo/bar', 'bar/foo'] }
+  let(:binding) { SpecTemplateContext.new('foo') }
+
+  it 'returns a tilt template' do
+    expect(subject.render_partial('index', html_types, binding)
+          ).to be_kind_of(String)
+  end
+
+  it 'renders html content' do
+    expect(subject.render_partial('index', html_types, binding)
+          ).to match('success')
+  end
+
+  it 'returns a tilt template for different types' do
+    expect(subject.render_partial('index', json_types, binding)
+          ).to be_kind_of(String)
+  end
+
+  it 'renders json content' do
+    expect(subject.render_partial('index', json_types, binding)
+          ).to match("{text: 'success'}")
+  end
+
+  it 'returns an ArgumentError, if given template does not exist' do
+    expect {
+      subject.render_partial('foobar', html_types, binding)
+    }.to raise_error(ArgumentError, /Template 'foobar' does not exist/)
+  end
+
+  it 'returns an ArgumentError, if no template fits types' do
+    expect {
+      subject.render_partial('index', foo_types, binding)
+    }.to raise_error(
+      ArgumentError, /Template 'index' not found/)
+  end
+
+  it 'uses the context' do
+    expect(subject.render_partial('context', html_types, binding)
+          ).to match('foo')
+
+  end
+end

spec/unit/zero/renderer/render_spec.rb

@@ -13,38 +13,9 @@ describe Zero::Renderer, '#render' do
   let(:binding) { SpecTemplateContext.new('foo') }
 
   context 'with default layout' do
-    it 'returns a tilt template' do
-      subject.render('index', html_types, binding).should be_kind_of(String)
-    end
-
-    it 'renders html content' do
-      subject.render('index', html_types, binding).should match('success')
-    end
-
-    it 'returns a tilt template for different types' do
-      subject.render('index', json_types, binding).should be_kind_of(String)
-    end
-
-    it 'renders json content' do
-      subject.render('index', json_types, binding).should match("{text: 'success'}")
-    end
-
-    it 'returns an ArgumentError, if given template does not exist' do
-      expect {
-        subject.render('foobar', html_types, binding)
-      }.to raise_error(ArgumentError, /Template 'foobar' does not exist/)
-    end
-
-    it 'returns an ArgumentError, if no template fits types' do
-      expect {
-        subject.render('index', foo_types, binding)
-      }.to raise_error(
-        ArgumentError, /Template 'index' not found/)
-    end
-
-    it 'uses the context' do
-      subject.render('context', html_types, binding).should match('foo')
-
+    it 'renders the template' do
+      expect(subject.render('index', html_types, binding)
+            ).to match(/layoutfile[\n]*success/)
     end
   end